A 30-year IBM veteran, she added marketing and strategy oversight to her role last year. The move positioned her as one of the company's top two candidates to replace current CEO Sam Palmisano, and it worked. Rometty will be Big Blue's next CEO, replacing Palmisano in January.
Boardroom battles and power plays shaped this year's U.S. list, which boasts eight new faces and -- surprise! -- a new No. 1.
